Abstract:

Since Grootegeluk Coal Mine commenced operation in 1980 all plant discards and inter-burden material have been stacked on discards dumps, a practice that has led to the spontaneous combustion of the waste material on these dumps. From 1980 to 1988 many large-scale and laboratory tests were conducted to determine the factors that contribute to spontaneous combustion, but no successful method of preventing or containing the problem was formulated. Further research into this problem during 1988 by a new team led to the project ‘Safe backfilling of the waste material into the operating pit at Grootegeluk Coal Mine’, which was included in the Coaltech 2020 portfolio of projects and also comprised SIMRAC Project COL713. Existing problems and past failures were re-analysed and all contributing factors identified. Reactivity tests of all waste materials and investigations of the contributing factors culminated in the construction of a reactivity model. A mathematical risk model was also constructed to evaluate methods of waste handling, based on the existing database of information as well as on all contributing factors.